I'd be pleasantly surprised if Xenoblade's US release outsold the Japanese release at all, much less with just preorders. I'm not entirely sure what the Japanese sales are though since I haven't seen anything for 2011, but I heard OpRainfall actually caused a bump in Japanese sales. May or may not be true, or meaningful.
I think it has the potential to do pretty well, word of mouth is definitely there. Nintendo isn't doing much to push the game though, and I don't shop at Gamestop so I don't know if they're doing much either.